[gtkada] Bug with Float'Image

[Duncan Sands]

Try using GNAT.Float_Control.Reset:

   procedure Reset;

   --  Reset the floating-point processor to the default state needed to get
   --  correct Ada semantics for the target. Some third party tools change
   --  the settings for the floating-point processor. Reset can be called
   --  to reset the floating-point processor into the mode required by GNAT
   --  for correct operation. Use this call after a call to foreign code if
   --  you suspect incorrect floating-point operation after the call.
   --
   --  For example under Windows NT some system DLL calls change the default
   --  FPU arithmetic to 64 bit precision mode. However, since in Ada 95 it
   --  is required to provide full access to the floating-point types of the
   --  architecture, GNAT requires full 80-bit precision mode, and Reset makes
   --  sure this mode is established.
   --
   --  Similarly on the PPC processor, it is important that overflow and
   --  underflow exceptions be disabled.
   --
   --  The call to Reset simply has no effect if the target environment
   --  does not give rise to such concerns.